Cobalt silicide has emerged as a common contact material for forming contacts to silicon in CMOS devices, due to its low resistivity, high stability, and small lattice mismatch with silicon. Moreover, as compared to many other contact materials (including other metal silicides, such as titanium silicide), cobalt silicide can be readily patterned into relatively small dimensions.
Unfortunately, the ongoing trend toward smaller device sizes in semiconductor fabrication processes is currently testing the limitations of cobalt silicide technology. In particular, as polysilicon gate lengths decrease, it becomes increasingly challenging to form uniform layers of cobalt silicide on these gates. Indeed, at dimensions below about 50 nm, extensive voiding occurs in cobalt silicide films, so that uniform cobalt silicide films cannot be formed in a reproducible manner.
There is thus a need in the art for a method for forming silicided polysilicon gates which overcomes the aforementioned infirmity. In particular, there is a need in the art for forming silicided polysilicon gates in which the gates have dimensions below 50 nm. These and other needs may be met by the devices and methodologies described herein.